Flowers pollinated by the wind are generally inconspicuous and often lack a corolla. The anthers are exposed to the wind and provided with much pollen, while the surface of the stigma may be long and feathery. Such flowers may also lack odor, nectar, and bright color. Can you tell why? Imperfect Flowers.--Some flowers, the wind-pollinated ones in particular, are imperfect; that is, they lack either stamens or pistils. Again, in some cases, imperfect flowers having stamens only are alone found on one plant, while those flowers having pistils only are found on another plant of the same kind. In such flowers, cross-pollination must of necessity follow. Many of our common trees are examples. [Illustration: The flower of "Lady Washington" geranium, in which stamens and pistil ripen at different times, thus insuring cross-pollination. _A_, flower with ripe stamens; _B_, flower with stamens withered and ripe pistil.] Other Cases.--The stamens and pistil ripen at different times in some flowers. The "Lady Washington" geranium, a common house plant, shows this condition. Here also cross-pollination must take place if seeds are to be formed. Summary.--If we now collect our observations upon flowers with a view to making a summary of the different devices flowers have assumed to prevent self-pollination and to secure cross-pollination, we find that they are as follows:-- _(1) The stamens and pistils may be found in separate flowers, either on the same or on different plants._ _(2) The stamens may produce pollen before the pistil is ready to receive it, or vice versa._ _(3) The stamens and pistils may be so placed with reference to each other that pollination can be brought about only by outside assistance._ Artificial Cross-pollination and its Practical Benefits to Man.--Artificial cross-pollination is practiced by plant breeders and can easily be tried in the laboratory or at home. First the anthers must be carefully removed from the bud of the flower so as to eliminate all possibility of self-pollination. The flower must then be covered so as to prevent access of pollen from without; when the ovary is sufficiently developed, pollen from another flower, having the characters desired, is placed on the stigma and the flower again covered to prevent any other pollen reaching the flower. The seeds from this flower when planted _may_ give rise to plants with the best characters of each of the plants which contributed to the making of the seeds. REFERENCE BOOKS ELEMENTARY